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Astron. Astrophys. 350, L27-L30 (1999)

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2. Observations and data reduction

Sakurai's object has shown fast and massive changes in its spectrum as carbon bearing molecules have formed (Asplund et al. 1997; Kerber et al. 1997) very much comparable to V605 Aql (Clayton & de Marco 1997). We were the first to discover a strong infrared excess (Kimeswenger et al. 1997) as a direct result of mass loss (Kerber et al. 1999b). Using general and discretionary time on ISO we have obtained a homogeneous set of photometric observations spanning the full ISOCAM (Cesarsky et al. 1996) LW wavelength range and covering a full year from February 1997 to 1998 in four epochs, closely monitoring the evolution of Sakurai's object in the mid-IR, see Table 1 for a summary of the observations. The ISOCAM observations were performed in staring mode. The error for the flux is between 2 and 8 per cent, with the latter applying to filters LW 1, 4 & 5, which showed saturation in the central pixel for epoch 4. The data was reduced in the Cam Interactive Analysis (CIA) package (Ott et al. 1996). The reduction steps included deglitching, dark correction (time dependent model) and averaging over the stabilized part of the readouts. The images were flatfielded using the calibration file flatfields. Fluxes were determined with aperture photometry, corrected for the size of the PSF, and using conversion factors of the Off Line Processing (OLP) v7 calibration file. For details see Blommaert (1998).


Table 1. Log of the ISOCAM observations

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© European Southern Observatory (ESO) 1999

Online publication: October 4, 1999